Gas cluster reactor for anisotropic film growth

ABSTRACT

A method of forming a low temperature silicide film on a substrate includes supplying a source gas to a cluster formation chamber to form a gas cluster that is subsequently moved to an ionization-acceleration chamber to form a gas cluster ion beam (GCIB). The GCIB is injected into a processing chamber containing the substrate. A precursor gas is injected through an injection device located on a top portion of the processing chamber to form a silicide film on the substrate by bombarding the substrate with the GCIB in the presence of the precursor gas.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of and claims the benefit ofpriority of U.S. patent application Ser. No. 14/277,857, filed on May15, 2014 with the U.S. Patent and Trademark Office (USPTO), the contentsof which are herein incorporated by reference in its entirety.

BACKGROUND

The present invention generally relates to semiconductor manufacturingand more particularly to low-temperature silicide film growth.

Complementary metal-oxide-semiconductor (CMOS) technology is commonlyused for fabricating field effect transistors (FETs) as part of advancedintegrated circuits (IC), such as CPUs, memory, storage devices, and thelike. Most common among these may be metal-oxide-semiconductor fieldeffect transistors (MOSFETs). In a typical MOSFET, a gate structure maybe energized to create an electric field in an underlying channel regionof a substrate, by which charge carriers are allowed to travel throughthe channel region between a source region and a drain region. As ICscontinue to scale downward in size, the use of high carrier mobilitymaterials in the channel region may be considered to boost deviceperformance for the 14 nm node and beyond. Group III-V materials, suchas gallium arsenide (GaAs) and indium gallium arsenide (InGaAs), may bepotential candidates to replace silicon (Si) as the channel material.

SUMMARY

The ability to conduct low temperature silicide film growth as well asin-situ pre-clean of a substrate may facilitate implementing newgeneration Group III-V channel materials in current CMOS technology.

A method of forming a low temperature silicide film on a substrate mayinclude supplying a source gas to a cluster formation chamber to form agas cluster that may be moved to an ionization-acceleration chamber toform a gas cluster ion beam (GCIB). The GCIB may be injected into aprocessing chamber containing the substrate. A precursor gas may beinjected through an injection device into the processing chamber to forma silicide film on the substrate by bombarding the substrate with theGCIB in the presence of the precursor gas.

A method of performing in-situ cleaning of a substrate may includesupplying an etchant gas to a cluster formation chamber to form a gascluster that may be subsequently moved to an ionization-accelerationchamber to form a gas cluster ion beam (GCIB). The GCIB may be injectedinto a processing chamber containing the substrate and bombarding thesubstrate with the GCIB to remove contaminants on the substrate.

A gas cluster ion beam (GCIB) device may include a source gas clusterformation chamber, an ionization-acceleration chamber connected to thecluster formation chamber, a processing chamber connected to theionization-acceleration chamber, a precursor gas injection devicepositioned on a top portion of the processing chamber such that theprecursor gas is directed at a surface of a substrate contained withinthe processing chamber, and an opening between theionization-acceleration chamber and the processing chamber.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description, given by way of example and notintended to limit the invention solely thereto, will best be appreciatedin conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a gas cluster ion beam (GCIB)device, according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a GCIB device depicting forming agas cluster ion beam and injecting a precursor gas to form a silicidefilm on a substrate, according to an embodiment of the presentinvention; and

FIG. 3 is a cross-sectional view of a GCIB device depicting forming abroad gas cluster ion beam and injecting a precursor gas to form asilicide film on a substrate, according to an alternate embodiment ofthe present invention.

The drawings are not necessarily to scale. The drawings are merelyschematic representations, not intended to portray specific parametersof the invention. The drawings are intended to depict only typicalembodiments of the invention. In the drawings, like numbering representslike elements.

DETAILED DESCRIPTION

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it may be understood that the disclosed embodiments aremerely illustrative of the claimed structures and methods that may beembodied in various forms. This invention may, however, be embodied inmany different forms and should not be construed as limited to theexemplary embodiments set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete and will fully convey the scope of this invention to thoseskilled in the art.

In the following description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps, and techniques, in order to provide a thoroughunderstanding of the present invention. However, it will be appreciatedby one of ordinary skill of the art that the invention may be practicedwithout these specific details. In other instances, well-knownstructures or processing steps have not been described in detail inorder to avoid obscuring the invention. It will be understood that whenan element as a layer, region, or substrate is referred to as being “on”or “over” another element, it may be directly on the other element orintervening elements may also be present. In contrast, when an elementis referred to as being “directly on” or “directly over” anotherelement, there are no intervening elements present. It will also beunderstood that when an element is referred to as being “beneath,”“below,” or “under” another element, it may be directly beneath or underthe other element, or intervening elements may be present. In contrast,when an element is referred to as being “directly beneath” or “directlyunder” another element, there are no intervening elements present.

In the interest of not obscuring the presentation of embodiments of thepresent invention, in the following detailed description, someprocessing steps or operations that are known in the art may have beencombined together for presentation and for illustration purposes and insome instances may have not been described in detail. In otherinstances, some processing steps or operations that are known in the artmay not be described at all. It should be understood that the followingdescription is rather focused on the distinctive features or elements ofvarious embodiments of the present invention.

As the semiconductor industry continues to scale down the size ofdevices, a new generation of high carrier mobility channel materialshave been considered to further improve device performance. Group III-Vmaterials, such as GaAs and InGaAs, may be potential candidates toreplace Si as the channel material. However, fabricating low resistancecontacts on source and drain regions formed in these Group III-Vmaterials may pose challenges to their implementation. One possiblechallenge may include forming a low resistance silicide on a complexmaterial such as InGaAs. In such cases, the physical properties of theGroup III-V materials may require a deposition temperature lower than400° C. when forming a silicide, which may in turn limit the choice ofsilicide materials. Therefore, formation of self-aligned silicidecontacts using traditional methods, which may include metal filmdeposition and high temperature annealing, may not be compatible withsilicide film growth on Group III-V materials.

Current technologies, such as gas cluster ion beam (GCIB) processes, mayexhibit unique nonlinear effects that may be valuable for surfaceprocessing applications, and in particular, low-temperature silicidefilm formation. By adding an injection device to a processing chamber ofa GCIB device, embodiments of the present disclosure may, among otherpotential benefits, conduct a low-temperature anisotropic depositionsuch that a highly conductive silicide film may be grown directly on asurface of the Group III-V material. This low-temperature anisotropicdeposition may reduce silicide contact resistance and potentiallyimprove device performance.

The present invention generally relates to semiconductor manufacturingand more particularly to low-temperature silicide film growth. Alow-temperature silicide film deposition may be conducted by modifying aGCIB device. One way to modify the GCIB device to conductlow-temperature silicide film growth may include adding an injectiondevice to a processing chamber of the GCIB device. One embodiment bywhich to form the silicide film on a Group III-V material surface usingthe modified GCIB device is described in detail below by referring tothe accompanying drawings in FIGS. 1-2.

Referring now to FIG. 1, a gas cluster ion beam (GCIB) device 100 isshown, according to an embodiment of the present disclosure. In thedepicted embodiment, the GCIB device 100 may include a cluster formationchamber 102, an ionization-acceleration chamber 108 and a processingchamber 110 in which a substrate 126 may be placed to be processed. Anaperture 114 may control the size of a subsequently formed gas clusterion beam. The aperture 114 may have a width capable of creating acollimated gas cluster ion beam as described in FIG. 2.

The GCIB device 100 may be configured to produce a gas cluster ion beamsuitable for treating the substrate 126. In the depicted embodiment, thesubstrate 126 may include a semiconductor wafer made from any of severalknown semiconductor materials including, but not limited to, silicon,germanium, silicon-germanium alloy, carbon-doped silicon, carbon-dopedsilicon-germanium alloy, and compound (e.g. Group III-V and Group II-VI)semiconductor materials. Non-limiting examples of compound semiconductormaterials include GaAs, InAs and/or InGaAs. In one exemplary embodiment,the substrate 126 may include GaAs.

The GCIB device 100 may further include an injection device 120 locatedon a top portion of the processing chamber 110. The injection device 120may be positioned relative to the substrate 126. More specifically, theposition of the injection device 120 may allow directional injection ofa subsequently inserted precursor gas for localized treatment of thesubstrate 126. In one embodiment, the injection device may be positionedon an angle of approximately 45° with respect to the plane of thesubstrate 126. However, it should be noted that the injection device 120may be positioned at any inclination angle that may allow localizedtreatment of areas of the substrate 126. The injection device 120 mayinclude, for example, a showerhead device having a plurality of openingsthrough which the precursor gas may flow.

Referring now to FIG. 2, a source gas 204 may be supplied to the clusterformation chamber 102 to form a gas cluster beam (not shown) that may besubsequently ionized and accelerated in the ionization-accelerationchamber 108 to form a gas cluster ion beam 208 (hereinafter “GCIB”). TheGCIB 208 may be used to form a silicide film 230 on the substrate 126contained in the processing chamber 110.

The processing steps involved in the formation of the GCIB 208 are wellknown to those skilled in the art and may include forming a gas clusterin the cluster formation chamber 102 by expansion of the source gas 204at high pressure through a room temperature nozzle (not shown) intovacuum. Then, gas clusters may enter the ionization-acceleration chamber108 located downstream of the cluster formation chamber 102. Once in theionization-acceleration chamber 108, a second vacuum stage may takeplace where gas clusters may be ionized by electron bombardment and thenaccelerated to a high potential ranging from approximately 1 keV toapproximately 100 keV. The energy range of the GCIB 208 may varyaccording to the envisioned use for the GCIB device 100. For the purposeof silicide film growth, the GCIB 208 may have an energy range varyingfrom approximately 10 keV to approximately 60 keV.

In some embodiments, magnetic filtering of the GCIB 208 may be conductedprior to a subsequent vacuum stage performed in the processing chamber110 in order to reduce monomer ion contamination. The resulting beam mayinclude cluster ions with a size distribution that may range from a fewhundred atoms to several thousand atoms. In one embodiment, the GCIB 208size distribution may vary between approximately 100 atoms/cluster toapproximately 20,000 atoms/cluster. In another embodiment, the GCIB 208size distribution may vary between approximately 5,000 atoms/cluster toapproximately 10,000 atoms/cluster.

At this point, a neutralizer assembly (not shown) connected to theprocessing chamber 110 may inject low energy electrons into the GCIB 208in order to decrease space charge blow-up and to avoid charge build-upon nonconductive substrates. When the GCIB 208 enters the processingchamber 110, mechanical scanning may be used for uniform treatment ofthe substrate 126. In some embodiments, a Faraday current monitor (notshown) may be used for dose control of the GCIB 208. The dose of GCIB208 may range from approximately 1 e¹² clusters/cm² to approximately 1e¹⁸ clusters/cm².

Depending upon the application, the gas clusters may be produced from avariety of gases. For the purpose of silicide film growth, the sourcegas 204 may include any metal or silicon-containing gas suitable forsilicide formation. In one embodiment, the source gas 204 may include asilicon-source gas such as SiH₂Cls (DCS), Si₂H₆, SiCl₄ and SiHCl₃. Inanother embodiment, the source gas 204 may include a metal-source gassuch as TiCl₄, WF₆, and metal amidinates, including cobalt and nickelbased amidinates.

With continued reference to FIG. 2, a precursor gas 210 may beintroduced into the processing chamber 110 through the injection device120. The precursor gas 210 may be directionally injected in order toreach a surface of the substrate 126. The precursor gas 210 may includeany metal or silicon containing gas suitable for silicide formation. Inone embodiment, the precursor gas 210 may include a silicon-source gassuch as SiH₂Cls (DCS), Si₂H₆, SiCl₄ and SiHCl₃. In another embodiment,the precursor gas 210 may include a metal-source gas such as TiCl₄, WF₆,and metal amidinates, including cobalt and nickel based amidinates.

It should be understood that if the source gas 204 includes asilicon-source gas, the precursor gas 210 may include a metal-source gasand vice versa.

In one embodiment, the precursor gas 210 and the GCIB 208 may besimultaneously injected into the processing chamber 110 for processingof the substrate 126. In this embodiment, simultaneous cluster ionbombardment and precursor gas exposure may occur on the substrate 126,adhesion of atoms (or molecules) of the precursor gas 210 on thesubstrate 126 may be predominantly facilitated by the energetic clusterions which may induce a chemical reaction at the substrate surface topromote growth of the silicide film 230. Therefore, the growth rate ofthe silicide film 230 may be controlled by the GCIB 208 flux.

It should be noted that, in embodiments where the precursor gas 210 andthe GCIB 208 may be simultaneously injected into the processing chamber110, the precursor gas 210 and the GCIB 208 may collide prior toreaching the substrate 126. These collisions may cause the gas clustersto lose energy before reaching the substrate 126 which may affect thedeposition process. In order to reduce collisions between the precursorgas 210 and the GCIB 208, pressure in the processing chamber 110 may bekept low enough such that collisions are minimized. For example,pressure in the processing chamber 110 may be kept in a range varyingfrom approximately 10⁻⁶ Ton to approximately 10⁻² Torr in order tominimize collisions between the precursor gas 210 and the GCIB 208 priorto reaching the substrate 126.

In another embodiment, the precursor gas 210 may be introduced to theprocessing chamber 110 in cycles of precursor gas injection followed byGCIB injection and vice versa. Stated differently, a cyclic depositionin which pulses of precursor gas 210 injection followed by GCIB 208bombardment may be conducted to form the silicide film 230 on thesubstrate 126. It should be noted that growth of the silicide film 230may occur layer by layer. In this embodiment, one or more monolayers ofthe precursor material on the substrate surface may react with theincoming energetic gas cluster ions, which may result in growth of thesilicide film 230. The thickness of the silicide film 230 may becontrolled by the number of precursor gas 210 and GCIB 208 pulses.

The processing chamber 110 may further include a mechanical scanningsystem which may allow the substrate 126 to move in different directionsso that the entire surface of the substrate 126 may be reached by theGCIB 208 and the precursor gas 210. As a result, a silicide film 230having a substantially even thickness may be formed on the substrate126.

It should be understood that the terms “growth and/or deposition” and“formed and/or grown” mean the growth of a material on a depositionsurface such as the substrate 126.

The GCIB 208 together with the precursor gas 210, injected via theinjection device 120 in the processing chamber 110, may provide alow-temperature thin-film deposition process that may facilitate theformation of a silicide film on the substrate 126 with enhanced density,adhesion, smoothness, crystallinity, and electrical characteristics thatsilicide films deposited by typical deposition techniques may notexhibit. Also, because the GCIB process is anisotropic, the silicidefilm may be substantially deposited in surfaces perpendicular to thedirection of the GCIB 208, having minimal impact on surfaces of thesubstrate 126 that are parallel to the GCIB 208.

In another embodiment, the GCIB 208 may be used to conduct an in-situpre-clean of the substrate 126 prior to forming the silicide film 230.Pre-cleaning of the substrate 126 may remove contaminants and produce auniform substrate surface which may benefit further processing steps,including the formation of the silicide film 230. In this embodiment,the source gas 204 may include any suitable etchant gas such as, forexample, NF₃.

Another embodiment by which to modify the GCIB device to conductlow-temperature suicide film growth on a Group III-V material isdescribed in detail below by referring to the accompanying drawing inFIG. 3. The present embodiment may include modifying an aperture of theprocessing chamber and adding an injection device to the processingchamber of the GCIB device.

Referring now to FIG. 3, a broad GCIB 320 may be formed in the GCIBdevice 300, according to an alternate embodiment of the presentdisclosure. In this embodiment, the aperture 114 (FIG. 2) may bemodified such that it has a width capable of increasing the clusterdistribution size to form the broad GCIB 320. By doing so, the broadGCIB 320 may reach a substantially larger area of the substrate 126 thanthe GCIB 208 (FIG. 2). In an embodiment, the aperture 114 (FIG. 2) mayremain in place, but may be widened to form the broad GCIB 320. In thedepicted embodiment, the aperture 114 (FIG. 2) may be removed entirelyto form the broad GCIB 320 which may be able to bombard the entiresurface of the substrate 126. In embodiments where the broad GCIB 320may be formed, mechanical scanning of the substrate 126 may not berequired to achieve a uniform treatment of the substrate 126. It shouldbe understood that the broad GCIB 320 may be formed from a source gassimilar to the source gas 204 described above with reference to FIG. 2.

Furthermore, different pressure and nozzle size combinations may berequired to increase the broad GCIB 320 intensity and achieve a largerdistribution size. In one embodiment, the broad GCIB 320 sizedistribution may vary between approximately 100 atoms/cluster toapproximately 20,000 atoms/cluster. In another embodiment, the GCIB 320size distribution may vary between approximately 5,000 atoms/cluster toapproximately 10,000 atoms/cluster.

In the depicted embodiment, the broad GCIB 320 may include an energyrange varying from approximately 10 keV to approximately 60 keV and maybe injected in doses ranging from approximately 1 e¹² clusters/cm² toapproximately 1 e¹⁸ clusters/cm².

An injection device 340 may be added to the processing chamber 110.Similarly to the injection device 120 shown in FIG. 1, the injectiondevice 340 may be located on a top portion of the processing chamber110. The injection device 340 may be positioned relative to thesubstrate 126. However, unlike the injection device 120 (FIG. 1), theinjection device 340 may not necessarily allow directional injection ofa subsequently inserted precursor gas for treatment of the substrate126.

Next, a precursor gas 360 may be introduced into the processing chamber110 via the injection device 340. The precursor gas 360 may include anymetal or silicon containing gas suitable for silicide formation. In oneembodiment, the precursor gas 360 may include a silicon-source gas suchas SiH₂Cls (DCS), Si₂H₆, SiCl₄ and SiHCl₃. In another embodiment, theprecursor gas 360 may include a metal-source gas such as TiCl₄, WF₆, andmetal amidinates, including cobalt and nickel based amidinates.

In one embodiment, the precursor gas 360 and the broad GCIB 320 may besimultaneously injected into the processing chamber 110 for processingof the substrate 126. In another embodiment, the precursor gas 360 maybe introduced to the processing chamber 110 in cycles of precursor gasinjection followed by GCIB injection and vice versa.

In embodiments where the precursor gas 360 and the broad GCIB 320 may besimultaneously injected into the processing chamber 110, the precursorgas 360 may be injected until reaching a pressure at which the broadGCIB 320 and the precursor gas 360 may collide. Since collisions maycause the gas clusters to lose energy before reaching the substrate 126,pressure in the processing chamber 110 may be maintained low enough suchthat collisions between the precursor gas 360 and the broad GCIB 320 maybe reduced. For example, in one embodiment, the pressure in theprocessing chamber 110 may be kept in a range varying from approximately10⁻² Ton to approximately 10⁻¹ Torr in order to minimize the collisionsbetween the precursor gas 360 and the broad GCIB 320 prior to reachingthe substrate 126.

In another embodiment, the broad GCIB 320 may be used to conduct anin-situ pre-clean of the substrate 126 prior to forming a silicide film380. Pre-cleaning of the substrate 126 may remove contaminants andproduce a uniform substrate surface which may benefit further processingsteps, including the formation of the silicide film 380. In thisembodiment, the source gas 204 may include any suitable etchant gas suchas, for example, NF₃.

Therefore, by adding an injection device to a processing chamber of aGICB device, low temperature silicide growth may be conducted to form ahighly conductive silicide film on a substrate that may include GroupIII-V materials. As a result, electrical resistance may be reduced,thereby enhancing device performance and potentially increasing productyield and reliability. Additionally, in-situ pre-clean of the substratemay be conducted to improve surface conditions prior to deposition ofthe silicide film.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiment, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A gas cluster ion beam (GCIB) device, the devicecomprising: a source gas cluster formation chamber; anionization-acceleration chamber connected to the cluster formationchamber; a processing chamber connected to the ionization-accelerationchamber; a precursor gas injection device positioned on a top portion ofthe processing chamber such that the precursor gas is directed at asurface of a substrate contained within the processing chamber; and anopening between the ionization-acceleration chamber and the processingchamber.
 2. The GCIB device of claim 1, wherein the injection devicecomprises a device having a plurality of openings through which theprecursor gas may flow.
 3. The GCIB device of claim 1, furthercomprising: a mechanical scanning system in the processing chamber. 4.The GCIB device of claim 1, further comprising: an aperture in theopening, the aperture having a width capable of forming a collimatedGCIB.
 5. The GCIB device of claim 4, wherein the opening has a widthcapable of forming a broad GCIB.